Cellulose is an important constituent in plants and comprises anhydrous glucose units. Unmodified cellulose is often difficult to use in applications due to limited solubility and complex crystalline structure. To overcome this problem cellulose is derivatized, and then it's physical properties are changed and it can be used in many materials, medical and food applications.
The derivatization of cellulose is complicated due to the resistibility of the material. When cellulose is derivatized it is difficult to control the degree of substitution and the yield in the process. Groups may also be uneven distributed along the cellulose chain which may give quality problems (Kamide K (2005) “Cellulose and Cellulose Derivatives” Elsevier ISBN 10: 0-444-82254-2).
There are several known ways to dissolve cellulose for various applications including manufacture regenerated cellulosic fiber. Often expensive chemicals are used in such processes. (Ohno H and Fukaya Y (2009)Task specific ionic liquids for cellulose technology Chemistry Letters V38)
Zhao et al, in Biotechnology and Bioengineering, pp. 1320-1328, Vol. 99, No. 6, 2008 discloses treatment of wood fiber bundles with NaOH and NaOH/Urea. There is disclosed treatment with cold NaOH. The treated pulp is neutralized. Any cellulose which is dissolved in the NaOH solution is apparently not used further. It is disclosed that treatment with cold NaOH is advantageous. The yield is improved with pretreatment.
WO 2008/095098 discloses a process for the manufacture of sugar from biomass, where the biomass is pretreated with alkali solution to improve the following hydrolysis. The temperature is increased and is 50-150° C., preferably 80-140° C.
Jeihanipour et al, in Biorecource Technology, pp. 1007-1010, Vol. 100, 2009 discloses alkali pretreatment of cotton linter followed by enzymatic hydrolysis. It is disclosed that low temperatures improves the process. The cellulose material which is used is not dissolved or suspended in the alkali solution, it remains solid. A problem in this technology is that some of the cellulose material dissolves and is discarded, which reduces the yield.
EP 0 344 371 A1 discloses a method for the production of monosaccharides by hydrolysis of lignocellulosic materials. There is no dissolution of the cellulose, where the dissolved cellulose is recovered. The cellulose is washed, but cellulose that is dissolved is apparently not recovered.
U.S. Pat. No. 4,089,745 discloses a process for enzymatic conversion of corn hull cellulose to glucose. Again there is no dissolution of the cellulose, where the dissolved cellulose is recovered. The cellulose is washed, but cellulose that is dissolved is apparently not recovered.
US 2008/0102502 A1 concerns recovery of inorganic salt during processing of lignocellulosic feedstocks. It is mentioned that carbon dioxide can be used to adjust pH.
There is a need for an improved process for the derivatization of cellulose.